Generally, various types of process gases are used in the manufacturing process of a semiconductor circuit. In a semiconductor manufacturing device for manufacturing semiconductor devices using process gases, the process conditions are monitored so as to process semiconductor wafers stably and accurately. The process conditions to be monitored include the process gas flow rates, the pressure and temperature in the process chamber, the RF power, the RF reflected wave, the voltage of electrostatic chuck, and the coolant gas pressure.
FIG. 1 is a schematic view of the entire structure of a semiconductor manufacturing device including a conventional monitoring device. The semiconductor manufacturing device shown in FIG. 1 includes a RF plasma processing device 2, a controller 4 for controlling each operation of the semiconductor manufacturing device, a power source unit 6, a process gas supply device 8, and a gas flow meter 10. These devices are arranged in a housing 12, and function in cooperation with one another as one semiconductor manufacturing device.
The RF plasma processing device 2 carries out a predetermined process using plasma on a process object to be processed (e.g., a semiconductor wafer). The process object to be processed is subjected to the plasma processing in a process chamber 2a. Process gas is supplied as a plasma source from the process gas supply device 8 into the process chamber 2a. Other various gases for controlling the process environment in the process chamber 2a are also supplied to the process chamber 2a. The flow rates of the process gas and the other various gases supplied into the process chamber 2a are measured and monitored by the gas flow meter 10.
As a result of the processing of the process object, exhaust gas is generated in the process chamber 2a. Below the process chamber 2a, a turbo molecular pump (TMP) 2b is provided to suck the exhaust gas from the process chamber 2a and then discharge the exhaust gas to an exhauster 14. The exhaust gas is then exhausted from a dry pump 16 via the exhauster 14 to a device such as a cleaning device (not shown).
In the semiconductor manufacturing device having the above structure, various sensors are provided in the RF plasma processing device 2, so as to monitor the process conditions. More specifically, the RF power and its reflected wave supplied to the RF plasma processing device 2 are monitored. The pressure and the temperature in the process chamber 2a of the RF plasma processing device 2 are also monitored. Furthermore, an electrostatic chuck for securing the process object to be processed (a semiconductor wafer) is provided in the process chamber 2a, and the voltage supplied to the electrostatic chuck is monitored. Also, the temperature of coolant gas that is supplied to the electrostatic chuck and controls the temperature of the electrostatic chuck is monitored. In the turbo molecular pump 2b for exhausting gas from the process chamber 2a, the pressure of the exhaust gas is monitored.
While monitoring those conditions, the semiconductor manufacturing device controls each of the process conditions in the semiconductor manufacturing process, so that a desired process is carried out for the process object that is being processed.
In the above conventional monitoring device, each of the process conditions is individually detected and controlled. More specifically, a reference value and a tolerable range are set for each of the process conditions, and a control operation is performed by adjusting the process condition to the reference value or maintaining the process condition within the tolerable range. Here, each of the process conditions is individually controlled, and the correlations between the process conditions are not taken into consideration and therefore are not monitored.
An actual process carried out for a process object is affected by the process conditions closely interrelated with one another. When a large number of process objects are continuously processed, the process conditions affects one another, and the result of the actual process on the process objects might change beyond the tolerable range, even if the process conditions change with time only within the tolerable range. In such a case, even though the actual process conditions as a whole change beyond the normal tolerable range, the process for the process objects are determined to be properly carried out, just because each of the process conditions is within each corresponding tolerable range.
In a semiconductor manufacturing device using the above conventional monitoring device and method, each process object after a process is subjected to test analysis to determine whether the process object is a proper product, i.e., whether the process has been properly performed. In other words, in a semiconductor manufacturing device using the conventional monitoring device, whether the process conditions are in a normal state cannot be checked before an actual process is completed.
A test on a processed object requires a certain period of time. For instance, when a large number of process objects are continuously processed, processed ones are stored until the process for the last process one is completed, and all the processed objects are then subjected to test analysis at once. In this manner, even though the process conditions as a whole move outside the normal range, the process is continued, as long as each of the process conditions is within each corresponding tolerable range. As a result, a large number of process objects are processed under the abnormal process conditions.